Fuel system differences in '97+ XJ's?

[PowerRam1987]

yeah its a 96 only part. a few people on here have done the switch over to plastic before. nothing i find when searching has any specifics on which wires to make fuel level sender function though

 

[kastein]

Here's the general run down
-96 First year, the ecu has no security or check-sum routines and very few people can flash these, uses the onboard tach driver for the cluster.
-97 First year for the checksum and security routines, also the first year for a CCD driven gauge cluster
-98 Minor mapping differences between the 97 ecu.
-99 First year for jtec+, switched from a resistive oil pressure sensor to a 0-5v oil pressure sender, the code is completely different from the earlier jtecs.
-00 They added 2 more ignition drivers to run the ignition cassette and made a few minor mapping changes.
-01 Other then a few minor mapping changes it's pretty much the same as an 00 cali emissions ecu.

Feel free to correct me or add to anything here.

I also have a feeling that if you run E15 in a jeep it will push the fuel trims further into the + range and might even throw a lean mixture code. Right now on E10 I'm at +6% on my long term fuel trims.

This is real interesting data, especially since I seem to recall my 98 having the later style sender. I'll have to check on that tomorrow if I remember.

Also, I have a JTEC sitting here that I pried open to reverse engineer it a few years ago. Never got around to it... IIRC, it came from a 99 4.0L AW4 NP231 C8.25 D30 equipped XJ.
Specs:
* part number P56041 493AE (cross refs to a '99 XJ ER0 DG0 California Emissions JTEC. ER0 = 4.0L DG0 = AW4)
* motorola SN 87A7868QDA9V
* module SN TEM1409QDA9V JBSAD
* the last three entries were on a label applied over a previous label, so I suspect either it's been reflashed or the underlying label was a generic JTEC label and the top label is the drivetrain-specific one applied after the firmware was loaded.
* CPU is a Motorola SC435407MFC22
* Flash chip is an Intel AB28F200 2mbit 128kx16 or 256kx8 SmartVoltage Boot Block flash EEPROM
* there is a Phillips chip marked 04827393AA (Chrysler part number :doh nearby - probably some sort of I/O interface/control chip
* there is a Motorola chip marked SC418371MFU4 5143340U02 (c) 97 CHRYSLER nearby - my bet, I/O interface/control chip
* there are three 74HC4066 quad bilateral switch chips nearby. Not sure what they're connected to.
* there are two 74HC14A hex Schmitt trigger inverter chips nearby.
* Near the '14As, there is an LM2901D quad comparator chip.
* Near the '4066s and the Phillips chip, there is an STMicroelectronics 4651537 chip. This is a funky power dissipating package and is near some inductors, electrolytics, and a small transformer so I am betting on it being a DC/DC converter control chip.
- moving to the other side of the flexboard, near the 3 interface connectors:
* there is an STMicroelectronics chip marked 4652166 near what appear to be the pads for the ignition coil drivers.
* There is also a Motorola SC370606DW chip. I suspect this is some sort of bus driven general purpose I/O chip, probably used to control the ignition coil drivers
* There is a D2PAK package component labeled 731M01. I can't find a datasheet, but it is the only populated pattern out of a row of 8 identical patterns, so I'm damn certain this is the ignition coil driver.
* there is a SOT 223 package chip made by Motorola with part number 43U02 near the SC370606DW. Not sure what it does.
* there are 6 more 43U02s on the other side of the STMicroelectronics 4652166. Each has a few 0805 size SMD resistors and two SOT23 parts next to it. I would put money on these being the low-side injector drivers.
* near those, there is a SOT 223 package made by Motorola labeled V3055. This is probably an NPN power transistor for... I'm not sure what. I would have to guess the evap purge solenoid but take that with a grain of salt...
* Near that, there is another 74HC14A hex Schmitt trigger inverter chip.
* Near the 3 interface connectors, there are three Intersil Corp CA3252M quad gated non-inverting power driver chips. Bets? I bet they're for the various relay drives, maybe the idle air control step motor driver, etc.
* Right next to those there are two STMicroelectronics 4651644s. More Chrysler proprietary part numbers, dammit!
* Right next to the connectors there's a Phillips 4651148. This is another proprietary part number but some googling tells me it's the CCD bus interface chip.
* Next to that an STMicroelectronics 4651606. If the Intersil chips don't handle the IAC stepper, this almost certainly does.
* Near the connectors, a part marked 317M. Probably an LM317 voltage regulator chip for the MAP, IAC, IAT, TPS, etc sensor reference voltage.
* Near the Intersil chips, a Motorola in a DPAK marked 912 305 5VL. Voltage regulator? No idea just guessing.
* Near the STMicro chips near the Intersil chips, there is a D2PAK Motorola part marked T 30 N06VL R901. No idea.

EDIT - found some more info. Apparently there are 3 CPUs, one is 16 bit (the one I IDed as the CPU) and can be reflashed, the other two are 8 bit for spark/fuel control and cannot be reflashed, at least that's what the factory manuals say. http://dodgeram.org/tech/repair/Pcm_diags/Page1.htm

More info and another reverse engineer who is further along, I'm going to ignore this thread and see how far I can get without using their info: http://thespeedfreaks.net/showthread.php?7503-Open-Source-JTEC-tunning

If Chrysler would stop having their chip suppliers mark the parts being sent to Motorola for JTEC assembly with custom part numbers that don't show up in my datasheet search engines, I'd have this damn thing halfway reverse engineered already.

Not to hijack this thread but quick question. In my 96 xj 4.0 ax15 i've replaced my steel tank bc it was rotted but now i'm on sending unit/pump assembly number 3. They keep rotting out as well. Going to switch to a 1997 plastic tank and sender/pump. I know it will plug in fine/strap in just the same and pump fuel as long as i modify fuel feed and vapor lines. As i understand it i can make the sender read fuel at half the actual level which works good enough for me. I searched around a bit for diagrams but i'm not seeing anything. Does anyone know which wires i have to splice? If not a fsm should be able to help me here for factory diagrams?

been there done that... you probably read my post about it. You need the rubber fill hoses that came with the plastic tank since the barbs on teh metal and plastic tanks are different sizes. Your gauge will read about halfway low and won't really be linear, I just filled up every 250 miles. Everything else worked great.

IIRC - double check this - the black wire is ground, that's easy. The wire on the body side of the connector that is green with a white stripe (again, I may be misremembering this) is +12 to the pump. The other two are the sender, I wouldn't even bother hooking it up. On the pump side for the late model plastic tank's sender, there are two heavy wires and two thin wires, the two thin ones are the sender and the two thick ones are the pump. The orange? one is +12, the other is ground. Might be red and black. Either way, it's fairly self explanatory.

The 96 level sender is a goofy device - I'm holding my old rotten one in my hand right now, actually. It's got 5 wires as you're already aware:
* black - connects to metal frame - ground
* orange - pump power
* purple / white or grey / white - mine is faded from sitting in the sun - part of the level sender ceramic resistance module wiring.
* yellow - part of the level sender ceramic resistance module wiring.
* pink / black - appears to go to one of the level sender float wiper terminals.

Basically, the sender in effect has two variable resistors in it, instead of just one. This is (iirc, I haven't read my 96 FSM in a while) to handle the fact that the 96 gauge cluster has a difference in the design of the low fuel warning light or something.

Level sender resistor 1, closer to the pivot point:
* stator (ceramic resistance module) terminal is the yellow wire.
* rotor/wiper terminal is grounded.
* resistance increases as tank empties. Sorry, don't have measurements, they're in the FSM IIRC (instrument panel section, last page probably) and I can give measuring them a shot if needed.

Level sender resistor 2, further from the pivot point:
* stator (ceramic resistance module) terminal is the purple/white wire.
* rotor/wiper terminal is pink/black wire.
* resistance increases as tank empties. No measurements here, same deal.

Purple/white looks like it might be gray/white or brown/white, mine has been sitting since early summer 09 when I removed it. It's pretty faded.